Method of preparing non-corrosive sulfurized terpenes and compositions containing the same



zniaisz Patented Oct. 27, 1959 lice Albert R. Sahel, Munster, Ind, assignor to Standard Oil Company, Chicago, lit, a corporation of Indiana No Drawing. Application February 27, 1957 Eierial No. 642,635

7 Claims. (Cl. 260- 139) This invention relates to improvements in corrosion inhibitors and the method of preparing the same, and more particularly relates to sulfurized terpenes having improved corrosion inhibiting properties, the method of preparing such improved sulfurized terpenes, and to lubricant compositions containing the improved sulfurized terpenes.

Advances in the design and construction of internal combustion engines to produce more efiicient and economical engines have presented many problems in the lubrication of such engines. To meet the increased severe demands upon engine lubricants, many types of lubricant additives have been developed to obtain certain desired properties and characteristics. For example, among the additives used to inhibit corrosion are the sulfurized terpenes, such as dipentenes. The sulfurized terpenes can be used alone in the lubricant composition, but are more frequently used in combination with detergent-type additives such as the neutralized reaction products of a phosphorus sulfide and a hydrocarbon.

While the sulfurized terpenes effectively inhibit corrosion to metals of the type used in most internal combustion engines, such sulfurized terpenes are corrosive to silver and silver alloys which have in recent years been used in certain heavy duty engines such as diesel engines.

It is an object of the present invention to provide a sulfurized terpene which is substantially non-corrosive to silver and similar metal. It is another object of the invention to provide a sulfurized terpene which is an effective corrosion inhibitor and which is non-corrosive to silver and similar metal. Still another object of the present invention is to provide a method of rendering sulfurized terpenes non-corrosive to silver and similar metals. Another object of the invention is to provide a method of preparing sulfurized dipentene which is substantially noncorrosive to silver and which has improved corrosion inhibiting properties. A further object of the invention is to provide a lubricant composition containing a sulfurized terpene having improved corrosion inhibiting characteristics and which is non-corrosive to silver, silver alloys and similar metal.

Other objects and advantages of the invention Will become apparent from the following description thereof.

In accordance with the present invention, the foregoing objects can be attained by treating at a temperature of from about 32 F. to about 40 F. for a period of from about 30 minutes to about 180 minutes, preferably about 120 minutes, a sulfurized terpene, normally corrosive to silver, with from about 20% to about 30% of an alkane monobasic carboxylic acid containing from 1 to about 4 carbon atoms in the alkyl group, While bubbling anhydrous hydrogen chloride through the mixture during the treating period. To facilitate the handling and treating of the sulfurized terpene it is preferable to dilute the same with a suitable normally liquid low boiling hydrocarbon diluent such as hexane, pentane or any naphtha boiling below about 250 F. The acid treated sulfurized terpene is then kept at a temperature of from about 32 F. to about 40 F., preferably about 40 F. for about 3 to 5 hours, then washed with a dilute alkane alcohol solution, such as a 5% ethanol solution, to remove any formic acid, and the a1cohol-washed material then freed from the diluent by distillation or evaporation, heating the product to a temperature of from about 212 toabout 250 F., preferably about 220 F. Examples of suitable alkane monobasic carboxylic acids which. can be used in the present invention are formic acid, acetic acid, propionic acid, and butyric acid.

The sulfurized terpene which is treated] with the alkane monobasic carboxylic acid, in accordance with the present invention, can be prepared by sulfurizing the desired terpene by anyone of various well known sulfurization processes. An efficient sulfurization process is that described and claimed in US. 2,445,983, issued July 27, 1948, to R. W. Watson in which the terpene is added in the liquid phase to a body of molten sulfur maintained at a certain optimum temperature. Terpenes which can be sulfurized by this method, include the monocyclic, bicyclic and acyclic terpenes, as well as polyterpenes. Examples of species falling Within these classes of terpenes are pine oil, turpentine, cymene, alpha-pinene, betapinene, allo-ocimene, fenchenes, bornylenes, menthadienes such as limonene, dipentene, terpinene, terpinolenes and A -p-menthadiene, sesquiterpenes, diterpene, and polyterpenes having the general formula (G l-I Mixtures of such terpenes can also be employed in the invention. As described in the above patent, elemental sulfur is stirred at a temperature above its melting point, for ex ample at a temperature of about 325 F. to about 400 F., and preferably at a temperature of from about 350 F. to about 375 F., and the terpene slowly added in the liquid phase to the molten sulfur. To facilitate adequate stirring, it is advantageous to add a small amount of the terpene, preferably when the molten sulfur has reached a temperature of about 310 F.340 F., and the temperature then raised to the desired reaction temperature, for example 375 F. before the remaining portion of the terpene is added. Usually, the addition of about 5% of the terpene will be found adequate to facilitate adequate stirring; the remaining of the terpene being then added at the desired reaction temperature.

The sulfurized terpenes contain some active sulfur, as evidenced by the darkening of a copper strip submerged in about 0.5% solution of the sulfurized terpenes in a hydrocarbon oil maintained at a temperature of about 210 F. For certain uses such as lubricating oil additives, the presence of such active sulfur compounds in the sulfurized terpenes is undesirable. These so-called active sulfur compounds can be deactivated by treating the same with an alkali metal sulfide, such as sodium sulfide or with a mixture of an alkali metal sulfide and a small amount of an alkaline material such as for example sodium hydroxide.

Among other sulfurization processes which can suitably be employed is that of treating the terpene with sulfur and hydrogen sulfide in the presence of water or steam at temperatures within the range of about 250 F. to 450 F. and at pressures up to about 1500 pounds per square inch for a period of 1 to 10 hours. The sulfurized terpene can also be prepared by treating the desired terpene with a sulfur chloride, such as S Cl or SCI at a temperature within the range of about 60 F. to about 250 F, When the terpene is sulfurized with a sulfur chloride, the chlorine present in the sulfurized material can be removed by treating the sulfurized material in a bomb at a temperature of about 300 F. to about 400 F. with ammonia or other aqueous or alcoholic alkalies, alkali metal sulfides and polysulfides, such as a sodium sulfide, or other bases.

The treatment of sulfurized terpenes in accordance a with the present invention is illustrated by the following examples:

EXAMPLE I (a) The sulfurized terpene used in this example was a sulfurized dipentene obtained by sulfurizing dipentene with 40% sulfur at 360-385 F. and washing the resultant sulfurized product with a 17% solution of Na S to remove corrosive sulfur. The final sulfurized dipentene so prepared contained about 35.6% sulfur.

(b) The sulfurized dipentene obtained in (a) above, diluted with hexane, was treated with 20% formic acid at ice bath temperature (about 32 F.) while bubbling anhydrous HCl through the mixture for 2 hours. At the end of this time, the product was placed in a cold room at 40 F. for 4 hours and then washed with a 5% ethanol solution to remove formic acid. After removing the hexane by distillation, the product was heated to 220 F. for minutes. The treated sulfurized dipentene contained 35.2% sulfur.

The above described treated sulfurized terpenes while effective corrosion inhibitors, are non-corrosive with respect to silver and similar metals when used in combination with lubricant base oils, such as hydrocarbon oils, synthetic hydrocarbon oils, such as those obtained by the polymerization of hydrocarbons, such as olefin polymers, for example, polybutenes, polypropylene and mixtures thereof, etc.; synthetic lubricating oils of the alkyleneoxide type, for example, the Ucon oils, marketed by Carbide and Carbon Corporation, as well as other synthetic oils, such as the polycarboxylic acid ester type oils, such as the esters of adipic acid, sebacic acid, maleic acid, azelaic acid, etc. The herein-described sulfurized terpenes are effectively used in such lubricants in concentrations of from about 0.01% to about 10%, and preferably from about 0.1% to about 5%.

While the above-described treated sulfurized terpenes can be suitably employed alone in combination with a base oil, they are usually used in combination with other lubricant addition agents, which impart various desired characteristics to the base oil. Usually, these products are used in conjunction with detergent-type additives, particularly those which contain sulfur or phosphorus and sulfur. Such detergent-type additives are usually used in amounts of from about 0.02% to about 10%, and preferably from about 0.01% to about 5%. Among the phosphorus and sulfur-containing addition agents are the neutralized reaction products of a phosphorus sulfide, and a hydrocarbon, an alcohol and a ketone, an amine or an ester. Of the phosphorus sulfide reaction product, I prefer to employ the neutralized reaction products of a phosphorus sulfide, such as phosphorus pentasulfide and a hydrocarbon of the type described in U. S. 2,316,- 082 issued to C. M. Loane et al., April 6, v1943. As taught in this patent, the preferred hydrocarbon constituent of the reaction is a mono-olefin hydrocarbon polymer resulting from the polymerization of low molecular weight mono-olefin hydrocarbons, such as propylenes, butenes, amylenes or copolymers thereof. Such polymers may be obtained by the polymerization of mono-olefins of less than 6 carbon atoms in the presence of a catalyst, such as sulfuric acid, phosphoric acid, boron fluoride, aluminum chloride, or other similar halide catalysts of the Friedel-Crafts type.

The polymers employed are preferably mono-olefin polymers or mixtures of mono-olefin polymers and isomono-olefin polymers having molecular weights ranging from about 150 to about 50,000, or more, and preferably from about 500 to about 10,000. Such polymers can be obtained, for example, by the polymerization in the liquid phase of a hydrocarbon mixture containing monoolefins and isomono-olefins, such as butylene and isobutylene at a temperature of from about 80 F. to about 100 F. in the presence of a metal halide catalyst of the Friedel-Crafts type, such as for example, boron fluoride, aluminum chloride, and the like. In the preparation of these polymers, a hydrocarbon mixture containing isobutylene, butylenes and butanes recovered from petroleum gases especially those gases produced in the cracking of petroleum oils in the manufacture of gasoline can be used.

Another suitable polymer is that obtained by polymerizing in the liquid phase a hydrocarbon mixture comprising substantially C hydrocarbons in the presence of an aluminum chloride-complex catalyst. The catalyst is preferablyprepared by heating aluminum chloride with isooctane. The hydrocarbon mixture is introduced into the bottom of the reactor and passed upwardly through the catalyst layer, While a temperature of from about 50 F. to about 110 F. is maintained in the reactor. The propane and other saturated gases pass through the catalyst while the propylene is polymerized under these conditions. The propylene polymer can be fractionated to any desired molecular weight, preferably from about 500 to about 1000 or higher.

Essentially paraffinic hydrocarbons, such as bright stock residuums, lubricating oil distillates, petrolatums or paraflinic waxes may be used. There can also be employed the condensation products of any of the foregoing hydrocarbons, usually through first halogenating the hydrocarbons with aromatic hydrocarbons in the presence of anhydrous inorganic halides, such as aluminum chloride, zinc chloride, boron fluoride, and the like.

Examples of other high molecular weight olefinic hydrocarbons, which can be employed, are cetene (C cerotene (C melene (C and mixed high molecular weight alkenes obtained by cracking petroleum oils.

Other preferred olefins suitable for the preparation of the phosphorus sulfide reaction products are olefins having at least 20 carbon atoms in the molecule of which from about 13 carbon atoms to about 18 carbon atoms, and preferably at least 15 carbon atoms are in a long chain. Such olefins can be obtained by the dehydrogenation of paraffins, such as by cracking of paraffin waxes or by the dehalogenation of alkyl halides, preferably long chain alkyl halides, particularly halogenated paraflin waxes.

As a starting material there can be used the polymer or synthetic lubricating oil obtained by polymerizing unsaturated hydrocarbons resulting from the vapor phase cracking of paraffin waxes in the presence of aluminum chloride which is fully described in United States Patents Nos. 1,955,260, 1,970,402 and 2,091,398. Still another type of olefin polymer which may be employed is the polymer resulting from the treatment of vapor phase cracked gasoline and/or gasoline fractions with sulfuric acid or solid adsorbents, such as fullers earth, whereby unsaturated polymerized hydrocarbons are removed. The reaction products of the phosphorus sulfide and the polymers resulting from the voltolization of hydrocarbons as described, for example, in United States Patents Nos. 2,197,768 and 2,191,787 are also suitable.

Other hydrocarbons that can be reacted with a phos phorus sulfide are aromatic hydrocarbons, such as for example, benzene, naphthalene, toluene, xylene, diphenyl, and the like, or with an alkylated aromatic hydrocarbon, such as for example, benzene having an alkyl substituent having at least four carbon atoms, and preferably at least eight carbon atoms, such as a long chain paraflin wax.

The phosphorus sulfide-hydrocarbon reaction product can be readily obtained by reacting a phosphorus sulfide, for example, P 8 with the hydrocarbon at a temperature of from about 200 F. to about 500 F., and preferably from about 200 F. to about 400 F., using from about 1% to about 50%, and preferably from about 5% to about 25% of the phosphorus sulfide in the reaction. It is advantageous to maintain a non-oxidizing atmosphere, such as for example, an atmosphere of nitrogen pletely react with the hydrocarbon so that no further purification becomes necessary; however, an excess amount of phosphorus sulfide can be used and separated from the product by filtration or by dilution with a hydrocarbon solvent, such as hexane, filtering and subsequently removing the solvent by suitable means, such as by distillation. If desired, thereaction product can be further treated with steam at an elevated temperature of from about 100 F. to about 600 F.

The neutralized phosphorus sulfide-hydrocarbon reaction product can be obtained by treating the acidic reaction product with a suitable basic compound, such as hydroxide, carbonate, oxide or sulfide of an alkaline earth metal or an alkali metal, such as for example,

potassium hydroxide, sodium hydroxide, sodium sulfide,

calcium oxide, lime, barium hydroxide, barium oxide, etc. Other basic reagents can be used, such as for example, ammonia or an alkyl or aryl-substituted ammonia, such as amines. The neutralization of the phosphorus sulfidehydrocarbon reaction product is carried out preferably in a non-oxidizing atmosphere by contacting the acidic reaction product either as such or dissolved in a suitable solvent, such as naphtha with a solution of the basic agent. As an alternative method, the reaction product can be treated with solid alkaline compounds, such as KOH, NaOH, Na CO K CO CaO, BaO, Ba(OH) Na S, and the like, at an elevated temperature of from about 100 F. to about 600 F. Neutralized reaction products containing a heavy metal constituent such as for example, tin, titanium, aluminum, chromium, cobalt, zinc, iron, and the like, can be obtained by reacting a salt of the desired heavy metal with the phosphorus sulfide-hydrocarbon reaction product, which has been treated with a basic reagent, such as above described.

Other phosphorus sulfide-reaction products which can be used are the reaction products of a phosphorus sulfide and a fatty acid ester of the type described in US 2,399,243; the phosphorus sulfide-degras reaction products of Us. 2,413,332; the reaction product of an alkylated phenol with the condensation product of P 8 and turpentine of US. 2,409,877 and US. 2,409,878; the reaction product of a phosphorus sulfide and stearonitrile of US. 2,4l6,807; etc.

The improved non-corrosiveness property of sulfurized terpenes treated in accordance with the present invention toward silver and silver alloys is demonstrated by the data in Table I obtained by subjecting mixtures of a hydrocarbon oil, a detergent-type additive together with an untreated sulfurized terpene and a sulfurized terpene, treated in accordance with the present invention, to the following test, referred to as the modified E.M.D. test:

A silver strip 2 cm. x 5.5 cm. with a small hole at one end for suspension is lightly abraided with No. steel wool, wiped free of any adhering steel wool, washed with carbon tetrachloride, air-dried and then weighed to 0.1 milligram. 300 cc. of the oil to be tested is placed in a 500 cc. lipless glass beaker and the oil heated to a temperature of 300 F. (12 F.) and the silver test strip suspended in the oil so that the strip is completely immersed therein. The oil in the beaker is stirred by means of a glass stirrer operating at 300 rpm. At the end of twenty-four hours, the silver strip is removed, and while still hot, rinsed thoroughly with carbon tetrachloride and air-dried. The silver strip is immersed in a 10% potassium cyanide solution at room temperature until the silver surface assumes its original bright or silver appearance, and is then washed successively with distilled Water and acetone, air-dried and Weighed.

The following lubricant compositions were subjected to the above test:

Sample A.-A solvent-extracted SAE-30 mineral oil+3.3% of a barium-containing neutralized reaction product of P 8 and a polybutene of about 1000 molecular Weight+0.75% of sulfurized dipentene containing 35.6% sulfur prepared as in (a) of Example I, supra.

Sample B.-Same as Sample A but containing 0.75% of the formic acid-treated sulfurized dipentene containing 35.2% sulfur obtained as in (b) of Example I, supra.

Table 1 Sample: E.M.D. loss in mg.

A a- B 35 That the treatment of sulfurized terpenes in accordance with the present invention not only renders the sulfurized the nearest milligram. The cleaned copper-lead test specimen is suspended in a steel beaker, cleaned with a hot trisodium phosphate solution, rinsed with water, acetone and dried, and 250 grams of the oil to be tested, together with 0.625 gram lead oxide and 50 grams of a 30-35 mesh sand charged to the beaker. The beaker is then placed in a bath or heating block and heated to a temperature of 300 (22 F.), while the contents are stirred by means of a stirrer rotating at 750 rpm. The contents of the beaker are maintained at this temperature for twenty-four hours, after which the copperlead test specimen is removed, rinsed with naphtha, dried and weighed. The test specimen is then replaced in the beaker and an additional 0.375 gram of lead oxide added to the test oil. At the end of an additional twenty-four hours of test operation, the test specimen is again removed, rinsed and dried as before, and weighed. The test specimen is again placed in the beaker together with an additional 0.250 gram of lead oxide and the test continued for another twenty-four hours (seventy-two hours total). At the conclusion of this time, the test specimen is removed from the beaker, rinsed in naphtha, dried and weighed.

The loss in weight of the test specimen is recorded after each weighing.

The following lubricant compositions were subjected to the above test and the results obtained are tabulated in Table II.

SAMPLE A Solvent extracted SAE-30 mineral oil+1.65% potassum-containing neutralized reaction product of P 8 and a polybutene of about 1000 molecular weight-l-0.5% of an untreated sulfurized dipentene containing 35.6% sulfur obtained as in (a) of Example I, supra.

SAMPLE B Same as Sample A but-containing 0.5% of the formic acid-treated sulfurized dipentene containing 35.2% sulfur obtained as in (b) of Example 1, supra.

SAMPLE C Solvent extracted SAE-30 mineral oil+3.3% bariumcontaining neutralized reaction product of P 8 and a polybutene of about 1000 molecular Weight+0.'75% of an untreated sulfurized dipentene containing 35.6% sulfur obtained as in (a) of Example I, supra.

SAMPLE D' Same as Sample C but containing 0.75% of the formic acid-treated sulfurized dipentene containing 35.2% sulfur obtained as in (b) of Example I, supra,

The above data demonstrate that treating sulfurized terpenes with a low molecular weight alkane monobasic carboxylic acid improves its corrosion inhibiting properties.

In addition to the detergent-type additive and the treated sulfurized terpene, lubricant compositions can contain other additives such as antioxidants, pourpoint depressors, extreme pressure agents, V.I. improvers, etc.

Lubricant compositions containing the hereindescribed and claimed treated sulfurized terpene are being claimed in my co-pending divisional application Serial No. 781,199, filed December 18, 1958.

Unless'otherwise stated, percentages given herein and in the appended claims are weight percentages.

I claim:

1. The method comprising treating a sulfurized terpene, normally corrosive to silver, with from about 20% to about 30% of an alkane monobasic carboxylic acid, containing from 1 to about 4 carbon atoms in the alkyl group, at a temperature of from about 32 F. to about 40 F. for a period of from about 3 to about 5 hours, and washing the cooled reaction mixture with a dilute alkane alcohol solution to remove the alkane monobasic carboxylic acid, and heating the washed product at a temperature of from about 212 F. to about 220 F.

2. The method of claim 1 wherein the alkane monobasic carboxylic acid is formic acid and the alkane alcohol is ethanol.

3. The method of claim 1 wherein the sulfurized terpene is sulfurized dipentene.

4. The method comprising treating a sulfurized dipentene, normally corrosive to silver, with from about 20% to about formic acid at a temperature of about 32 F. While bubbling anhydrous HCl through said reaction mixture, maintaining the reaction mixture at a temperature of about F. for about 4 hours, washing the reaction mixture with about a 5% ethanol solution, and heating the product to a temperature of about 220 F.

5. The method comprising treating a hexane solution of a sulfurized dipentene, normally corrosive to silver, with about 20% formic acid at a temperature of about 32 F. while bubbling anhydrous HCl through said mixture, maintaining said formic acid-treated mixture at a temperature of about 40 F. for about 4 hours, washing the formic acid-treated mixture with about a 5% ethanol solution, removing the hexane from the washed formic acid treated sulfurized dipentene and then heating the treated sulfurized dipentene to a temperature of about 220 F.

6. The sulfurized terpene substantially non-corrosive to silver, obtained by the method of claim 1.

7. The sulfurized dipentene, substantially non-corrosive to silver, obtained by the method of claim 4.

References Cited in the file of this patent UNITED STATES PATENTS 2,768,157 Cashman et a1. Oct. 23, 1956 2,786,029 Brugman Mar. 19, 1957 2,786,829 Stevens et al. Mar. 26, 1957 2,800,450 Bondi et a1. July 23, 1957 

1. THE METHOD COMPRISING TREATING A SULFURIZED TERPENE, NORMALLY CORROSIVE TO SILVER, WITH FROM ABOUT 20% TO ABOUT 30% OF AN ALKANE MONOBASIC CARBOXYLIC ACID, CONTAINING FROM 1 TO ABOUT 4 CARBON ATOMS IN THE ALKYL GROUP AT A TEMPERATURE OF FROM ABOUT 32*F. TO ABOUT 40*F. FOR A PERIOD OF FROM ABOUT 32*F. TO ABOUT AND WASHING THE COOLED REACTION MIXTURE WITH A DILUTE ALKANE ALCOHOL SOLUTION TO REMOVE THE ALKANE MONOBASIC CARBOXYLIC ACID, AND HEATING THE WASHED PRODUCT AT A TEMPERATURE OF FROM ABOUT 212*F. TO ABOUT 220*F.
 6. THE SULFURIZED TERPENE SUBSTANTIALLY NON-CORROSIVE TO SILVER, OBTAINED BY THE METHOD OF CLAIM
 1. 